For sharpening knives, it is very important to keep a constant angle at which blade contacts sharpening device. Changing angle will result in mis-sharpening or damaging blade edge. Sharpening stones may have integrated angle guides, such as disclosed, for example, in U.S. Pat. Nos. 4,094,106; 4,197,677; 6,048,262; and 9,033,771. However, different knives have different shapes and need to be sharpened at different angles between the knife blade surface and the surface of the sharpening tool. Those disclosed sharpening guides or sharpening tools with angle guides have fixed guide angles. Therefore, a user will need multiple sharpening tools with different angles when the user has different knife blades to be sharpened.
Another issue of the disclosed sharpening tools with fixed angle guide is that their angle guides cannot be repositioned to another section of the sharpening tool when the section of the sharpening tool adjacent to the fixed angle guide has been worn out. Thus, the sharpening tools with fixed angle guide are inconvenient, cost-ineffective, and need large spaces to store multiple sharpening tools.
Furthermore, a sharpening tool, such as a sharpening stone, maybe in different height or be held by holders that have different height. An angle guide is best to be at the same level as the sharpening surface of the sharpening tool. Therefore, it is inconvenient as the traditional angle guide that has a fixed height.